One example of a laminated optical apparatus is a flat panel display such as a liquid crystal display (LCD). LCDs exist in a multitude of embodiments depending upon the specific type of liquid crystal material and the configuration of the polarizers and electrodes. In its simplest form, a typical LCD comprises a liquid crystal cell comprising a pair of optically transparent substrates, each of which has an outer surface to which additional optical films, including without limitation a polarizer or compensator layer, can be applied.
Many LCDs exhibit optical performance that is highly sensitive to the angle at which the display is viewed. Optical compensation layers, also referred to as compensators or retarders, are commonly used to mitigate the viewing angle effects in LCDs. Such a compensator or retarder layer may be applied directly to the outer surface of each substrate so as to be situated between the substrate and an associated polarizer layer.
Delamination of a layer applied to an LCD, including without limitation a compensator or polarizer layer laminated or adhesively bonded to a substrate, often occurs in LCDs. To improve the interfacial adhesive forces between the applied layer and the substrate, the layer-receiving surface of the substrate may be treated before application by, for example, plasma or corona discharge surface treatment, acid/base etching, or the like. These treatments are usually time-consuming and not always effective, particularly for certain substrates such as fluorinated compounds.
As an alternative to the foregoing surface treatments, adhesion promoters such as acrylic polymers (an example of which is General Electric's SHP401 primer) applied to the layer-receiving surface of the substrate have been used in an effort to prevent delamination. However, the interfacial forces provided by such adhesion promoters have often been inadequate to prevent delamination.
Another example of a laminated optical apparatus subject to delamination is the window or dome structure that houses the optical sensors carried by a missile. Such a dome structure may comprise a pair of adhesively bonded optically transparent sapphire substrates or layers. The severe operating environment of the missile subjects the dome structure to high temperatures and mechanical stresses often causing separation of the dome layers along the adhesive bond.